Conferencing is the capability of coupling information signals among three or more users in a communications system. The information signals are typically voice signals but, with the advent of multimedia communications capabilities, can also be nonvoice signals, i.e., data, video, facsimile and the like.
Signal compression techniques have long been used to reduce the bandwidth required for signal transmission. These techniques have been used for both voice and data signals.
When compressed information signals are conferenced using existing conference bridging techniques, the compressed signals are each decompressed, summed and this sum is then recompressed and broadcast to all conferees. The problem with this approach is that the tandeming, i.e., serial connection of signal coders and decoders to respectively compress and decompress the information signal, degrades the resulting signal quality to a level that, in trial studies, has been found to be objectionable to many conferees. Another problem is that the bridging apparatus can be costly, especially for conference bridging apparatus capable of conferencing a large number of conferees. At times, the signal degradation and/or the apparatus costs associated with conferencing equipment can exceed system objectives. At such times, the prior art solution has been to utilize only uncompressed signals. This solution, in turn, requires a higher bandwidth communications channel between any potential conferee and the conferencing apparatus. This requirement can be expensive or difficult to provide. This is especially true in communications system applications where the number of potential conferees is quite large. It would, therefore, be desirable if a conferencing arrangement could be devised for compressed signals which overcomes the limitations of the prior art.